1. Field of the Invention
The present invention relates to a spiral wound type membrane element employed for a membrane separation device such as a low-pressure reverse osmosis membrane separation device, an ultrafiltration device or a microfiltration device and methods of running and washing a spiral wound type membrane module.
2. Description of the Background Art
With recent applications of the membrane separation technology to water purification, the membrane separation technology is now applied as pretreatment for reverse osmosis membrane separation systems used desalination of seawater, for example. While a microfiltration membrane and an ultrafiltration membrane attaining high permeate flow rates are generally used for such membrane separation, a reverse osmosis membrane attaining a high permeate flow rate under ultra-low pressures of not more than 10 kgf/cm2 has recently been developed.
As a membrane element used for membrane separation, a hollow fiber membrane element is generally used in consideration of the membrane area (volumetric efficiency) per unit volume. However, the membranes of the hollow fiber membrane element are easy to break, and when the membranes are broken, raw water is mixed into the permeate to disadvantageously lower the separating performance.
On the other hand, a spiral wound type membrane element can provide a large, membrane area. The spiral wound type membrane element, which can maintain high separating performance, is superior in reliability to the hollow fiber membrane element.
FIG. 25 is a partially fragmented perspective view of a conventional spiral wound type membrane element 21, and FIG. 26 is a perspective view showing the appearance of the conventional spiral wound type membrane element 21.
As shown in FIG. 25, the spiral wound type membrane element 21 is formed by superposing separation membranes 26 on both surfaces of a permeate spacer (permeate passage forming member) 25 and bonding three sides thereby forming an envelope-like membrane (bag-like membrane) 23, mounting an opening of the envelope-like membrane 23 on a water collection pipe 22 formed by a perforated hollow pipe and spirally winding the envelope-like membrane 23 on the outer peripheral surface of the water collection pipe 22 with a netty raw water spacer (raw water passage forming member) 24.
The raw water spacer 24 is provided for forming a passage for the raw water along the envelope-like membrane 23. If the thickness of the raw water spacer 24 is small, the separation membranes 26 are clogged with suspended substances although the charging efficiency thereof is increased. In general, therefore, the thickness of the raw water spacer 24 is set to about 0.7 to 3.0 mm.
In relation to treatment of raw water such as river water containing a large quantity of suspended substances, a spiral wound type membrane element employing a zigzag corrugated sheet type raw water spacer (the so-called corrugated spacer) is already known in the art.
As shown in FIG. 26, the outer peripheral surface of the spiral wound type membrane element 21 is covered with a protective sheath 27 made of FRP (Fiber-Reinforced Plastics) or formed by a shrink tube, while packing holders 28 called anti-telescopes are mounted on both ends thereof respectively.
FIG. 27 is a sectional view showing an exemplary method of running the conventional spiral wound type membrane element 21. As shown in FIG. 27, a pressure vessel (pressure-resistant vessel) 30 is formed by a tubular case 31 and a pair of end plates 32a and 32b. The end plate 32a is provided with a raw water inlet 33, and the other plate 32b is provided with a concentrate outlet 35. The end plate 32b is provided on its center with a permeate outlet 34.
The spiral wound type membrane element 21 having a packing 37 mounted on a portion close to an end of the outer peripheral surface is introduced into the tubular case 31, and both opening ends of the tubular case 31 are sealed with the end plates 32a and 32b respectively. One opening end of the water collection pipe 22 is engaged with the permeate outlet 34 of the end plate 32b, while an end cap 36 is attached to the other opening end thereof.
In order to run the spiral wound type membrane element 21, raw water 51 is introduced into a first liquid chamber 38 from the raw water inlet 33 of the pressure vessel 30. As shown in FIG. 27, the raw water 51 is supplied from one end of the spiral wound type membrane element 21. The raw water 51 axially flows along the raw water spacer 24, and is discharged as concentrate 53 from the other end of the spiral wound type membrane element 21. The raw water 51 permeating through the separation membranes 26 along the raw water spacer 24 flows into the water collection pipe 22 as permeate 52 along the permeate spacer 25, and is discharged from the end of the water collection pipe 22.
The permeate 52 is taken out from the permeate outlet 34 of the pressure vessel 30 shown in FIG. 27. The concentrate 53 is taken out from a second liquid chamber 39 of the pressure vessel 30 through the concentrate outlet 35.
When the spiral wound type membrane element 21 is run, the membrane 23 is clogged with suspended substances contained in the raw water 51, to reduce the membrane flux. Therefore, chemical washing is performed for eliminating such clogging and recovering the membrane flux. However, such chemical washing requires much labor and a high cost. In order to prevent clogging, therefore, back wash reverse filtration is periodically performed with permeate or air in a hollow fiber membrane element, for example.
In the conventional spiral wound type membrane element 21, however, back wash reverse filtration results in the following problems:
FIG. 28 is a partially fragmented perspective view showing back wash reverse filtration in the conventional spiral wound type membrane element 21. As shown in FIG. 28, the permeate 52 is introduced from an end of the water collection pipe 22. Since the outer peripheral surface of the envelope-like membrane 23 wound around the water collection pipe 22 is covered with the protective sheath 27, the permeate 52 derived from the outer peripheral surface of the water collection pipe 22 permeates through the envelope-like membrane 23 and axially flows in the spiral wound type membrane element 21 along the raw water spacer 24, and is discharged from the end of the spiral wound type membrane element 21. Despite back wash reverse filtration, therefore, contaminants such as turbid substances causing clogging of the membrane 23 are readily captured by the raw water spacer 24 before discharged from the end of the spiral wound type membrane element 21 and insufficiently removed.
As shown in FIG. 27, further, the clearance between the inner peripheral surface of the tubular case 31 of the pressure vessel 30 and the spiral wound type membrane element 21 defines a dead space S, to cause residence of the fluid (fluid residue). When the spiral wound type membrane element 21 is used over a long period, the fluid residing in the dead space S is denatured. Particularly when the fluid contains organic matter, germs such as microorganisms may propagate to decompose the organic matter and give off a bad smell or decompose the separation membranes 26, leading to reduction of reliability.
In addition, the raw water 51 is supplied from one end of the conventional spiral wound type membrane element 21 and discharged from the other end, and hence the conventional spiral wound type membrane element 21 requires the packing holders 28 for prevent the envelope-like membrane 23 wound around the water collection pipe 22 from being deformed in the form of a bamboo shoot. Further, pressure loss caused by the raw water spacer 24 as well as by clogging results in pressure difference between thee raw water inlet side and the concentrate outlet side, to deform the spiral wound type membrane element 21. In order to prevent such deformation, the outer peripheral surface of the envelope-like membrane 23 wound around the water collection pipe 22 is covered with the protective sheath 27 made of FRP or formed by a shrink tube. Thus, the component cost and the manufacturing cost are increased.
In order to prevent formation of cake with contaminants contained in the raw water 51, further, it is necessary to attain a sufficient linear velocity on the membrane surface with a sufficient flow rate on the concentrate side. When the flow rate is increased on the concentrate side, however, recovery per spiral wound type membrane element is reduced while a large pump is required for supplying the raw water 51, to remarkably increase the system lost.
An object of the present invention is to provide a highly reliable spiral wound type membrane element which can reduce the cost and is easy to wash, and a method of running a spiral wound type membrane module.
Another object of the present invention is to provide a washing method capable of readily and reliably removing contaminants captured by a spiral wound type membrane element.
(1) First Invention
In a method of running a spiral wound type membrane element according to an aspect of the first invention, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in running, and introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe from at least the outer peripheral portion of the spiral wound type membrane element in washing.
According to the method of running a spiral wound type membrane element, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in running. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element from the system in back wash reverse filtration. Therefore, the separated contaminants are discharged with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed for regularly maintaining a stable permeate flow rate in running.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The running method may further comprise a step of discharging the washing liquid from at least the outer peripheral portion of the spiral wound type membrane element and thereafter axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element in washing. Thus, contaminants adhering to at least the outer peripheral portion of the spiral wound type membrane element can be readily separated while the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged from the system.
Alternatively, the running method may further comprise a step of axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element before introducing the washing liquid from at least one opening end of the perforated hollow pipe. Also in this case, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily separated and the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged from the system.
Alternatively, the running method may further comprise a step of axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element in parallel with introduction of the washing liquid from at least one opening end of the perforated hollow pipe. Also in this case, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily separated and the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged from the system.
In the running method, the liquid-permeable material of the spiral wound type membrane element may be a separation membrane. In this case, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and the outer peripheral portion of the spiral membrane component is covered with the separation membrane, whereby contaminants are captured on the separation membrane covering at least the outer peripheral portion of the spiral wound type membrane element. Therefore, the contaminants can be uniformly removed, by back wash reverse filtration with permeate or the like, for example.
Further, only contaminants smaller than the pore size of the separation membrane covering the outer peripheral portion infiltrate into the clearances between the envelope-like membranes forming the spiral membrane component, whereby loads on the envelope-like membranes are reduced to enable stable running over a long period.
In addition, the separation membrane may be a microfiltration membrane. In this case, contaminants larger than the pore size of the microfiltration membrane are captured on the outer peripheral portion of the spiral membrane component, not to infiltrate into the spiral membrane component.
The separation membrane may be an ultrafiltration membrane. In this case, contaminants larger than the pore size of the ultrafiltration membrane are captured on the outer peripheral portion of the spiral membrane component, not to infiltrate into the spiral membrane component.
In the running method, the liquid-permeable material forming the spiral wound type membrane element may be a net. Even if contaminants captured on the outer peripheral portion of the spiral membrane component increase back pressure caused in back wash reverse filtration, the net covering the outer peripheral portion prevents the spiral membrane component from swelling, not to increase the spaces between the envelope like membranes in this case. Thus, the envelope-like membranes are prevented from breakage resulting from swelling, so that contaminants contained in the raw liquid do not leak into the permeated liquid.
The net may be made of synthetic resin or metal.
The net preferably has at least three meshes and not more than 200 meshes. Thus, the spiral membrane component can be reliably inhibited from swelling caused by back pressure in back wash reverse filtration, and the raw liquid can be sufficiently supplied to the clearances between the envelope-like membranes forming the spiral membrane component from the outer peripheral side in running.
In the running method, a prescribed portion of the net covering the outer peripheral portion of the spiral membrane component may be reinforced with resin along the circumferential direction. Thus, even if high back pressure is caused in back wash reverse filtration, the net covering the outer peripheral portion reliably prevents the spiral membrane component from swelling.
In the running method, the spiral wound type membrane component may further include a permeate passage forming member inserted between the envelope-like membranes and extended outward from the outer peripheral side of the envelope-like membranes so that the extended portion of the permeate passage forming member is wound around the outer peripheral surface of the spiral membrane component as a net.
In this case, the spiral membrane component can be prevented from swelling caused, by back pressure in back wash reverse filtration while suppressing an additional component cost.
In the running method, the thickness of the outer peripheral passage forming member of the spiral wound type membrane element may particularly be at least 0.6 mm and not more than 30 mm. Thus, contaminants adhering to at least the outer peripheral portion of the spiral wound type membrane element can be discharged from the system in back wash reverse filtration while maintaining high volumetric efficiency of the spiral wound type membrane element with respect to the pressure vessel.
In the running method, the outer peripheral passage forming member may be so arranged that a raw liquid substantially linearly flows substantially in parallel with the axial direction of the perforated hollow pipe. Thus, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be substantially linearly washed away substantially in parallel with the axial direction of the perforated hollow pipe with the raw liquid with small pressure loss in back wash reverse filtration of the spiral wound type membrane element. Therefore, the contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily and reliably discharged from the system.
The outer peripheral passage forming member may be formed by a netty passage forming member. In this case, the netty passage forming member sufficiently protects the outer peripheral portion of the spiral wound type membrane element and prevents the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion thereof. Further, the raw liquid can readily infiltrate into the clearances between the envelope-like membranes through the netty passage forming member from the outer peripheral portion of the spiral wound type membrane element. Thus, handleability of the spiral wound type membrane element is further improved and it is possible to efficiently supply the raw liquid between the envelope-like membranes while reliably capturing contaminants on the outer peripheral portion of the spiral wound type membrane element.
In the running method, the discharging step may include using a permeated liquid as the washing liquid.
In a method of running a spiral wound type membrane element according to another aspect of this invention, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane element, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element, for performing dead end filtration. In this case, contaminants are captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element, and the supplied raw liquid can be recovered as the permeated liquid with recovery of 100% in theory.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid while the scale of the equipment can be reduced due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The aforementioned method of running a spiral wound type membrane element is particularly effective for treating a raw liquid having low turbidity (content of contaminants).
The running method may further comprise a step of introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element in washing.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element from the system in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and a constant permeate flow rate can be regularly maintained in running.
In a method of running a spiral wound type membrane element according to still another aspect of this invention, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element while regularly or periodically feeding a partial raw liquid axially along the outer peripheral portion of the spiral wound type membrane element and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane element, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. It is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element by regularly or periodically forming a flow of the raw liquid axially along the outer peripheral portion of the spiral wound type membrane element. Thus, the spiral wound type membrane element can be stably run over a long period.
A flow of the raw liquid is axially formed in the clearance between the spiral wound type membrane element and the pressure vessel, whereby no dead space is defined to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The aforementioned method of running a spiral wound type membrane element is particularly effective for treating a raw liquid having high turbidity (content of contaminants).
In the running method, the supplying step may include a step of returning the partial raw liquid to the supply side again. In this case the partial raw liquid is regularly or periodically fed axially along the outer peripheral portion of the spiral wound type membrane element, whereby it is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element.
The discharged raw liquid is circulated, whereby the supplied raw liquid can be recovered as the permeated liquid with recovery of 100% in theory.
The aforementioned method of running a spiral wound type membrane element is particularly effective for obtaining a permeated liquid from a raw liquid having high turbidity with high recovery.
In a method of washing a spiral wound type membrane element according to a further aspect of this invention, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element.
In the aforementioned spiral wound type membrane element, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the system with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
The washing method may further comprise a step of axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element after discharging the washing liquid from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily separated and the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged from the system.
Alternatively, the washing method may further comprise a step of axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element before introducing the washing liquid from at least one opening end of the perforated hollow pipe. Also in this case, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily separated and the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged from the system.
Alternatively, the washing method may further comprise a step of axially feeding a raw liquid along the outer peripheral portion of the spiral wound type membrane element in parallel with introduction of the washing liquid from at least one opening end of the perforated hollow pipe. Also in this case, contaminants adhering to the outer peripheral portion of the spiral wound type membrane element can be readily separated and the contaminants separated from the spiral wound type membrane element cane be readily and reliably discharged from the system.
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and a raw liquid outlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in running, and introducing a washing liquid from at least one opening end of the perforated hollow pipe, discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe from at least the outer peripheral portion of the spiral wound type membrane element and taking out the washing liquid from the pressure vessel through the raw liquid inlet or the raw liquid outlet in washing.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in running. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe of the spiral wound type membrane element in the spiral wound type membrane module, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged from the spiral wound type membrane module with the washing liquid. Therefore, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and a constant permeate flow rate can be regularly maintained in running.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions With no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel for performing dead end filtration and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, and the supplied raw liquid can be recovered as the permeated liquid with recovery of 100% in theory.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid while the scale of the equipment can be reduced due to dead end filtration. Thus, the system cost is reduced.
Pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The aforementioned method of running a spiral wound type membrane module is particularly effective for treating a raw liquid having low turbidity (content of contaminants).
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and a raw liquid outlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel while regularly or periodically feeding a partial raw liquid axially along the outer peripheral portion of the spiral wound type membrane element for taking out the partial raw liquid from the pressure vessel through the raw liquid outlet and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element. It is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element by regularly or periodically forming a flow of the raw liquid axially along the outer peripheral portion of the spiral wound type membrane element. Thus, the spiral wound type membrane module can be stably run over a long period.
A flow of the raw liquid is axially formed in the clearance between the spiral wound type membrane element and the pressure vessel, whereby no dead space is defined to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The aforementioned method of running a spiral wound type membrane module is particularly effective for treating a raw liquid having high turbidity.
In the running method, the supplying step may include a step of supplying the raw liquid taken out from the pressure vessel through the raw liquid inlet again. In this case, the partial raw liquid is regularly or periodically fed axially along the outer peripheral portion of the spiral wound type membrane element, whereby it is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element.
Further, the discharged raw liquid is circulated, whereby the supplied raw liquid can be recovered as the permeated liquid with recovery of 100% in theory.
The aforementioned method of running a spiral wound type membrane module is particularly effective for obtaining a permeated liquid from a raw liquid having high turbidity with high recovery.
In a method of washing a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel.
In the spiral wound type membrane element of the aforementioned spiral wound type membrane module, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the system with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
(2) Second Invention
In a method of running a spiral wound type membrane element according to an aspect of this invention, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying raw liquid from at least the outer peripheral side of the spiral wound type membrane element and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in running, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element in washing, and setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period to not more than 600.
According to the method of running a spiral wound type membrane element, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in running, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to at least the outer peripheral portion of the spiral wound type membrane element from the system in back wash reverse filtration. Therefore, the separated contaminants are discharged from the system with the washing liquid. Thus, contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed for regularly maintaining a stable permeate flow rate in running.
Further, it is possible to prevent a separation membrane from application of an excessive load, remove contaminants adhering to the outer peripheral portion by performing sufficient washing, and stably run the spiral wound type membrane element over a long period with high filtration efficiency by setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope like membranes in the washing period to not more than 600.
It is preferable to supply the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day, and set the filtration time to at least 10 minutes and not more than 300 minutes. Further, it is preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 4.0 m3/m2/day, and set the washing time to at least 10 seconds and not more than 300 seconds. In such ranges, the permeate flow rate in filtration, the filtration time, the washing liquid flow rate in washing land the washing time are so set that the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period is not more than 600.
In particular, it is more preferable to supply the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day, and set the filtration time to at least 10 minutes and not more than 30 minutes. Further, it is more preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 3.0 m3/m2/day, and set the washing time to at least 30 seconds and not more than 60 seconds. In this case, the ratio of the volume of the permeated liquid permeating through the envelope like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period is not more than 120.
It is possible to prevent the separation membrane from application of an excessive load while the outer peripheral portion is prevented from sedimentation of contaminants so that the spiral wound type membrane element can be stably run over a long period by setting the permeate flow rate in filtration and the filtration time as described above. Further, it is possible to efficiently obtain a target permeate flow rate.
Further, it is possible to sufficiently separate contaminants adhering to the outer peripheral portion so that the spiral wound type membrane element can be stably run continuously over a long period while reduction of filtration efficiency can be suppressed by setting the washing liquid flow rate in washing and the washing time as described above.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane element for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions width no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In the running method, the discharging step may include using a permeated liquid as the washing liquid.
In a method of washing a spiral wound type membrane element according to another aspect of this invention, the spiral wound type membrane element comprises a spiral membrane component including a perforate hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of taking out a permeated liquid by filtration and thereafter introducing a washing liquid from at least one opening end of the perforated hollow pipe for discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of, the spiral wound type membrane element, and setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope-like membranes in washing to not more than 600.
In the aforementioned spiral wound type membrane element, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the system with the washing liquid. Thus, the contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
Further, it is possible to prevent a separation membrane from application of excessive load, remove contaminants adhering to the outer peripheral portion by performing sufficient washing, and stably run the spiral wound type membrane element over a long period with high filtration efficiency by setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope like membranes in washing to not more than 600.
It is preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 4.0 m3/m2/day and set the washing time to at least 10 seconds and not more than 300 seconds when supplying the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day while setting the filtration time to at least 10 minutes and not more than 300 minutes.
In particular, it is more preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 3.0 m3/m2/day, set the washing time to at least 30 seconds and not more than 60 seconds and set the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope-like membranes in washing to not more than 120 when supplying the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day and setting the filtration time to at least 10 minutes and not more than 30 minutes.
Thus, it is possible to sufficiently separate contaminants adhering to the outer peripheral portion so that the spiral wound type membrane element can be stably run continuously over a long period and reduction of filtration efficiency can be suppressed.
In a method of running a spiral wound type membrane module according to still another aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passages forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in running, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel through the raw liquid inlet in washing, and setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period to not more than 600.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration in running. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to at least the outer peripheral portion of the spiral wound type membrane element from the system in back wash reverse filtration. Therefore, the separated contaminants are discharged from the system with the washing liquid. Thus, the contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed for regularly maintaining a stable permeate flow rate in running.
Further, it is possible to prevent a separation membrane from application of an excessive load, remove contaminants adhering to the outer peripheral portion by performing sufficient washing, and stably run the spiral wound type membrane module over a long period with high filtration efficiency by setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period to not more than 600.
It is preferable to supply the raw liquid so that the permeate flow rate infiltration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day, and set the filtration time to at least 10 minutes and not more than 300 minutes. Further, it is more preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 4.0 m3/m2/day, and set the washing time to at least 10 seconds and not more than 300 seconds. In such ranges, the permeate flow rate in filtration, the filtration time, the washing liquid flow rate in washing and the washing time are set so that the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period is not more than 600.
In particular, it is more preferable to supply the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day, and set the filtration time to at least 10 minutes and not more than 30 minutes. Further, it is more preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 3.0 m3/m2/day, and set the washing time to at least 30 seconds and not more than 60 seconds. In this case, the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in the running period to the volume of the washing liquid permeating through the envelope-like membranes in the washing period is not more than 120.
It is possible to prevent the separation membrane from application of an excessive load, contaminants are inhibited from sedimentation on the outer peripheral portion, and the spiral wound type membrane module can be stably run continuously overlap long period by setting the permeate flow rate in filtration and the filtration time as described above.
Further, it is possible to sufficiently separate contaminants adhering to the outer peripheral portion so that the spiral wound type membrane module can be stably run continuously over long period and reduction of filtration efficiency can be suppressed by setting the washing liquid flow rate in washing and the washing time as described above.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In a method of washing a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of taking out a permeated liquid by filtration, thereafter introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel, and setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope-like membranes in washing to not more than 600.
In the aforementioned spiral wound type membrane module, at least the outer peripheral portion of the spiral wound type membrane element is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the system with the washing liquid. Thus, the contaminants captured on at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
Further, it is possible to prevent a separation membrane from application of an excessive load in the spiral wound type membrane element, remove contaminants adhering to the outer peripheral portion by performing sufficient washing, and stably run the spiral wound type membrane module continuously over a long period with high filtration efficiency by setting the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope-like membranes in washing to not more than 600.
It is preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 4.0 m3/m2/day and set the washing time to at least 10 seconds and not more than 300 seconds when supplying the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day and setting the filtration time to at least 10 minutes and not more than 300 minutes.
In particular, it is more preferable to introduce the washing liquid into the perforated hollow pipe so that the washing liquid flow rate in washing is at least 1.0 m3/m2/day and not more than 3.0 m3/m2/day, set the washing time to at least 30 seconds and not more than 60 seconds and set the ratio of the volume of the permeated liquid permeating through the envelope-like membranes in filtration to the volume of the washing liquid permeating through the envelope-like membranes in washing to not more than 120 when supply the raw liquid so that the permeate flow rate in filtration is at least 0.5 m3/m2/day and not more than 2.0 m3/m2/day and setting the filtration time to at least 10 minutes and not more than 30 minutes.
Thus, it is possible to sufficiently separate contaminants adhering to the outer peripheral portion so that the spiral wound type membrane module can be stably run continuously over a long period and reduction of filtration efficiency can be suppressed.
(3) Third Invention
In a method of running a spiral wound type membrane module according to an aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element at a constant flow rate through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the raw liquid is supplied to the spiral wound type membrane element at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In the running method, the supplying step may include a step of controlling the supply pressure for the raw liquid thereby controlling the flow rate of the raw liquid constant. Alternatively, a pressure pump may be provided on the raw liquid supply side of the spiral wound type membrane module, and the supplying step may include a step of controlling the flow rate of the raw liquid constant by controlling the output of the pressure pump. Thus the raw liquid is supplied to the spiral wound type membrane element at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
In the running method, the pressure vessel may further have a raw liquid outlet and the supplying step may include a step of regularly or intermittently taking out part of the raw liquid from the pressure vessel through the raw liquid outlet and returning at least part of the taken-out raw liquid to the supply side again.
In this case, a flow of the raw liquid is regularly or periodically formed axially along the outer peripheral portion of the spiral wound type membrane element and it is possible to inhibit contaminants contained in the raw liquid from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element. Thus, the spiral wound type membrane module can be more stably run over a long period.
Further, at least part of the taken-out raw liquid is returned to the supply side again, whereby the permeated liquid can be obtained with high recovery.
In a method of running a spiral wound type membrane module according to another aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe at a constant flow rate.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
The permeated liquid is taken out at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained. In the running method, the supplying step may include a step of controlling the flow rate of the permeated liquid constant by controlling the supply pressure or the supply flow rate of the raw liquid. Alternatively, a pressure pump may be provided on the raw liquid supply side of the spiral wound type membrane module, and the supplying step may include a step of controlling the flow rate of the permeated liquid constant by controlling the output of the pressure pump. Thus, the permeated liquid is taken out at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
In a method of running a spiral wound type membrane module according to still another aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element at a constant flow rate through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral side of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel in washing, and changing a washing condition in washing in response to change of the pressure on the raw liquid supply side of the spiral wound type membrane module or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element infiltration for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the raw liquid is supplied to the spiral wound type membrane element at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced. Further, pressures is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Therefore, the separated contaminants are discharged from the system with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, pressure on the raw liquid supply side exceeds that on the permeated liquid takeout side. Therefore, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type membrane element by changing the washing condition in washing in response to change of the pressure on the raw liquid supply side or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration. Thus, the spiral wound type membrane module can be stably run with high efficiency.
In the running method, the washing condition in the changing step is at least one of the supply flow rate of the washing liquid introduced into the perforated hollow pipe, the supply pressure for the washing liquid introduced into the perforated hollow pipe, the time interval for washing and the time of washing. It is possible to effectively wash the spiral wound type membrane module with high efficiency by changing at least one of these washing conditions in response to the degree of contamination of the spiral wound type membrane element.
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe at a constant flow rate in filtration, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral side of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel in washing, and changing a washing condition in washing in response to change of the pressure on the raw liquid supply side of the spiral wound type membrane module or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in filtration for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the permeated liquid is taken out at a constant flow rate, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration, whereby the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Therefore, the separated contaminants are discharged with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly discharged and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, pressure on the raw liquid supply side exceeds that on the permeated liquid takeout side. Therefore, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type membrane element by changing the washing condition in washing in response to change of the pressure on the raw liquid supply side or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration. Thus, the spiral wound type membrane module can be stably run with high efficiency.
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element with constant pressure through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe for taking out the washing liquid from the pressure vessel through at least the outer peripheral side of the spiral wound type membrane element in washing, and changing a washing condition in washing in response to change of the flow rate of the permeated liquid in filtration.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
The raw liquid is supplied with constant pressure, whereby the spiral wound type membrane module can be stably run.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is obtained.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed, and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, the flow rate of the obtained permeated liquid is reduced. Therefore, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type Membrane element by changing the washing condition in washing in response to change of the flow rate in filtration. Thus, the spiral wound type membrane module can be stably run with high efficiency.
In a method of running a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the method comprises steps of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel and taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral side of the spiral wound type membrane element for taking out the washing liquid from the pressure vessel in washing, and changing a washing condition in washing in response to change of the flow rate of the washing liquid taken out from the pressure vessel.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants tare captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the en elope-like membranes of the spiral wound type membrane element are reduced.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under thigh pressure. Thus, high pressure resistance is obtained.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed, and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, the flow rate of the washing liquid taken out from the pressure vessel is reduced in washing. Therefore, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type membrane element by changing the washing condition in washing in response to change of the flow rate of the washing liquid in washing. Thus, the spiral wound type membrane module can be stably run with high efficiency.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe, and a control system controlling the flow rate of the raw liquid supplied through the raw liquid inlet of the pressure vessel by the supply system constant.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the control system controls the flow rate of the raw liquid constant, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is obtained.
In the spiral wound type membrane module, the pressure vessel may further have a raw liquid outlet, and the spiral wound type membrane module may further comprise a circulation system regularly or intermittently taking out part of the raw liquid from the pressure vessel through the raw liquid outlet and returning at least part of the taken-out raw liquid to the supply side again.
In this case, it is possible to regularly or intermittently take out part of the raw liquid from the pressure vessel through the raw liquid outlet and form a flow of the raw liquid axially along the outer peripheral portion of the spiral wound type membrane element. Thus, it is possible to inhibit contaminants contained in the raw liquid from adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element and the spiral wound type membrane module can be more stably run over a long period. Further, the circulation system can return at least part of the taken-out raw liquid to the supply side again, whereby the permeated liquid can be obtained with high recovery.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe, and a control system controlling the flow rate of the permeated liquid taken out from at least one opening end of the perforated hollow pipe by the permeated liquid takeout system constant.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the control system controls the flow rate of the permeated liquid constant, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under thigh pressure. Thus, high pressure resistance is obtained.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel in filtration, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, a washing liquid introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe in washing, a washing liquid takeout system taking out the washing liquid discharged through at least the outer peripheral side of the spiral wound type membrane element from the pressure vessel in washing, and a control system controlling the flow rate of the raw liquid supplied to the raw liquid inlet of the pressure vessel by the raw liquid supply system in filtration constant while controlling a washing condition in washing in response to change of the pressure on the raw liquid supply side of the spiral wound type membrane module or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the control system controls the flow rate of the raw liquid constant, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is obtained.
In the spiral wound type membrane module, the washing liquid introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe in washing. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Therefore, the separated contaminants are discharged with the washing liquid. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, pressure on the raw liquid supply side exceeds that on the permeated liquid takeout side. In the aforementioned spiral wound type membrane module, the control system controls the washing condition in washing in response to change of the pressure on the raw liquid supply side or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side. Thus, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type membrane element, and the spiral wound type membrane module can be effectively washed with high efficiency.
In the spiral wound type membrane module, the control system may control at least one of the supply flow rate of the washing liquid introduced into the perforated hollow pipe by the washing liquid introduction system, the supply pressure for the washing liquid introduced into the perforated hollow pipe by the washing liquid introduction system, the time interval for washing and the time for washing. The control system controls at least one of these washing conditions in response to the degree of contamination of the spiral wound type membrane element, whereby the spiral wound type membrane module can be effectively washed with high efficiency.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel in filtration, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, a washing liquid introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe in washing, a washing liquid takeout system taking out the washing liquid discharged through at least the outer peripheral side of the spiral wound type membrane element from the pressure vessel in washing, and a control system controlling the flow rate of the permeated liquid taken out by the permeated liquid takeout system constant in filtration and controlling a washing condition in washing in response to change of the pressure on the raw liquid supply side of the spiral wound type membrane module or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side in filtration.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope -like membranes of the spiral wound type membrane element are reduced.
Further, the control system controls the flow rate of the permeated liquid constant, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is obtained.
In the spiral wound type membrane module, the washing liquid introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe in washing. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element infiltration, pressure on the raw liquid supply side exceeds that on the permeated liquid takeout side. In the aforementioned spiral wound type membrane module, the control system controls the washing condition in washing in response to change of the pressure on the raw liquid supply side or change of the pressure difference between the raw liquid supply side and the permeated liquid takeout side. Thus, it is possible to effectively wash the spiral wound type membrane module with high efficiency in response to the degree of contamination of the spiral wound type membrane element, and the spiral wound type membrane module can be stably run with high efficiency.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel in filtration, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, a washing liquid introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe in washing, a washing liquid takeout system taking out the washing liquid discharged through at least the outer peripheral side of the spiral wound type membrane element from the pressure vessel in washing, and a control system controlling the pressure of the raw liquid supplied to the raw liquid inlet of the pressure vessel by the raw liquid supply system in filtration while controlling a washing condition in washing in response to change of the flow rate of the permeated liquid in filtration.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes of the spiral wound type membrane element are reduced.
Further, the control system controls the pressure of the raw liquid constant, whereby the spiral wound type membrane module can be stably run.
In addition, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, where t y the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is obtained.
In the spiral wound type membrane module, the washing liquid introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, the flow rate of the obtained permeated liquid is reduced. In the aforementioned spiral wound type membrane module, the control system controls the washing condition in washing in response to change of the flow rate of the permeated liquid in filtration. Thus, the spiral wound type membrane module can be efficiently washed in response to the degree of contamination of the spiral wound type membrane element, and can be stably run with high efficiency.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel having a raw liquid inlet and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, and the spiral wound type membrane module further comprises a raw liquid supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through the raw liquid inlet of the pressure vessel in filtration, a permeated liquid takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe in filtration, a washing liquid introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe in washing, a washing liquid takeout system taking out the washing liquid discharged through at least the outer peripheral side of the spiral wound type membrane element from the pressure vessel in washing, and a control system controlling a washing condition in washing in response to change of the flow rate of the washing liquid taken out from the pressure vessel by the washing liquid takeout system in the washing.
In the spiral wound type membrane module, the raw liquid supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element in filtration, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelop e-like membranes of the spiral wound type membrane element are reduced.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel due to dead end filtration, to allow no residence of a fluid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a fluid containing organic matter, therefore, high reliability can be attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of organic matter and decomposition of separation membranes.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid due to dead end filtration. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
In the spiral wound type membrane module, the washing liquid introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe in washing. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element. The liquid-permeable material and the outer peripheral passage forming member prevent the spiral wound type membrane element from spreading between the envelope-like membranes on the outer peripheral portion, thereby ensuring a passage for discharging contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in back wash reverse filtration. Thus, the separated contaminants are discharged with the washing liquid. Therefore, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed and the spiral wound type membrane module can be stably run with high reliability.
When contaminants adhere to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element in filtration, the flow rate of the washing liquid taken out by the washing liquid takeout system in washing is reduced. In the aforementioned spiral wound type membrane module, the control system controls the washing condition in response to change of the flow rate of the washing liquid in washing. Thus, the spiral wound type membrane module can be effectively washed with high efficiency in response to the degree of contamination of the spiral wound type membrane element, and can be stably run with high efficiency.
(4) Fourth Invention
In a method of running a spiral wound type membrane module according to an aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has one or a plurality of liquid ports, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through any one of the one or a plurality of liquid ports and taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element. Thus, loads on the envelope-like membranes are reduced.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of the liquid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a liquid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under thigh pressure. Thus, high pressure resistance is attained.
In a method of running a spiral wound type membrane module according to another aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has a plurality of liquid ports, and the method comprises a step of supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through any one of the plurality of liquid ports of the pressure vessel, taking out a permeated liquid from at least one opening end of the perforated hollow pipe, and regularly or intermittently taking out part of the raw liquid from the pressure vessel through another one of the plurality of liquid ports.
According to the method of running a spiral wound type membrane module, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes are reduced.
Further, it is possible to regularly or intermittently form a flow of the raw liquid axially along the outer peripheral portion of the spiral wound type membrane element by taking out part of the supplied raw liquid from the pressure vessel. It is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element due to such a flow of the raw liquid, whereby the spiral wound type membrane module can be stably run over a long period.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of the liquid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a liquid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under thigh pressure. Thus, high pressure resistance is attained.
In the running method, the supplying step may include a step of returning at least part of the raw liquid taken out from the pressure vessel to the supply side again. In this case, at least part of the taken-out raw liquid can be circulated, whereby the permeated liquid can be obtained with high recovery.
In a method of washing a spiral wound type membrane module according to still another aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has one or a plurality of liquid ports, and the method comprises a step of introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element for taking out the washing liquid from the one or a plurality of liquid ports of the pressure vessel.
In the spiral wound type membrane element of the aforementioned spiral wound type membrane module, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from at least one liquid port of the pressure vessel with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
In the washing method, the washing liquid may be a permeated liquid, and the discharging step may include a step of returning at least part of the permeated liquid taken out from the pressure vessel to the raw liquid supply side again. In this case, at least part of the taken-out permeated liquid can be circulated, whereby the permeated liquid can be obtained with high recovery.
In a method of washing a spiral wound type membrane module according to a further aspect of this invention, the spiral wound type membrane module comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has a plurality of liquid ports, and the method comprises steps of introducing a washing liquid from at least one opening end of the perforated hollow pipe and discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element for taking out the washing liquid from any one or a plurality of ones of the plurality of liquid ports of the pressure vessel, and supplying a raw liquid into the pressure vessel through another one of the plurality of liquid ports and taking out the raw liquid from the pressure vessel through the aforementioned any one liquid port or still another liquid port.
In the spiral wound type membrane element of the aforementioned spiral wound type membrane module, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby the raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
When the washing liquid is introduced from at least one opening end of the perforated hollow pipe in washing, the washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from one or a plurality of liquid ports of the pressure vessel with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
Further, a flow of the raw liquid is formed axially along the outer peripheral portion of the spiral wound type membrane element by introducing the raw liquid into the pressure vessel and taking out the raw liquid. Thus, contaminants adhering to the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be readily and reliably separated and the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged, so that the spiral wound type membrane module can be more stably run.
The raw liquid may be fed axially along the outer peripheral portion of the spiral wound type membrane element before or after introducing the washing liquid from at least one opening end of the perforated hollow pipe for performing back wash reverse filtration. Alternatively, the raw liquid may be fed simultaneously with back wash reverse filtration.
In the washing method, the washing liquid may be a permeated liquid, the discharging step may include a step of returning at least part of the permeated liquid taken out from the pressure vessel to the raw liquid supply side, and the supplying step may include a step of returning at least part of the raw liquid taken out from the pressure vessel to the raw liquid supply side. In this case, at least part of the permeated liquid and the raw liquid taken out from the pressure vessel can be circulated, whereby the permeated liquid can be obtained with higher recovery.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has one or a plurality of liquid ports, and the spiral wound type membrane module further comprises a supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through any one of the one or a plurality of liquid ports of the pressure vessel, and a takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe.
In the spiral wound type membrane module, the supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element, for performing dead end filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes are reduced.
Further, no dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of the liquid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a liquid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from de composition of the organic matter, decomposition of separation membranes and the like.
In addition, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby, the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. Further, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
In addition, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has a plurality of liquid ports, and the spiral wound type membrane module further comprises a supply system supplying a raw liquid from at least the outer peripheral side of the spiral wound type membrane element through any one of the plurality of liquid ports of the pressure vessel, a first takeout system taking out a permeated liquid from at least one opening end of the perforated hollow pipe, and a second takeout system regularly or intermittently taking out part of the raw liquid from the pressure vessel through another one of the plurality of liquid ports.
In the spiral wound type membrane module, the supply system supplies the raw liquid from at least the outer peripheral side of the spiral wound type membrane element, for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element, whereby loads on the envelope-like membranes are reduced.
The second takeout system takes out part of the raw liquid supplied by the supply system from the pressure vessel, whereby a flow of the raw liquid can be regularly or intermittently formed axially along the outer peripheral portion of the spiral wound type membrane element. It is possible to inhibit contaminants contained in the raw liquid from adhering to at least the outer peripheral portion of the spiral wound type membrane element by such a flow of the raw liquid. Thus, the spiral wound type membrane module can be stably run over a long period.
No dead space is defined in the clearance between the spiral wound type membrane element and the pressure vessel, to allow no residence of the liquid in the clearance between the spiral wound type membrane element and the pressure vessel. Also when employing the spiral wound type membrane module for separating a liquid containing organic matter, therefore, high reliability is attained with no problems such as propagation of germs such as microorganisms, occurrence of a bad smell resulting from decomposition of the organic matter, decomposition of separation membranes and the like.
Further, the raw liquid is supplied from at least the outer peripheral side of the spiral wound type membrane element and pressure is applied to the spiral wound type membrane element from all directions with no pressure causing axial displacement, whereby the envelope-like membranes wound around the perforated hollow pipe are not deformed in the form of bamboo shoots. Thus, neither packing holders nor a protective sheath is required, whereby the component cost and the manufacturing cost are reduced. In addition, high recovery is attained without employing a large pump for supplying the raw liquid. Thus, the system cost is reduced.
Further, pressure is applied to the spiral wound type membrane element from all directions, whereby the spiral wound type membrane element is not deformed even if the raw liquid is supplied under high pressure. Thus, high pressure resistance is attained.
The spiral wound type membrane module may further comprise a circulation system returning at least part of the raw liquid taken out from the pressure vessel to the supply side again. In this case, the circulation system can circulate at least part of the taken-out raw liquid, whereby the permeated liquid can be obtained with high recovery.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has one or a plurality of liquid ports, and the spiral wound type membrane module further comprises an introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe, and a takeout system discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element and taking out the washing liquid through one or a plurality of liquid ports of the pressure vessel.
In the spiral wound type membrane element of the aforementioned spiral wound type membrane module, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby a raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
In the spiral wound type membrane module, the introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe in washing. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the liquid port of the pressure vessel through the takeout system with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
In the spiral wound type membrane module, the washing liquid may be a permeated liquid, and the spiral wound type membrane module may further comprise a circulation system returning at least part of the permeated liquid taken out from the pressure vessel to the raw liquid supply side. In this case, the circulation system can circulate at least part of the taken-out permeated liquid, whereby the permeated liquid can be obtained with high recovery.
A spiral wound type membrane module according to a further aspect of this invention comprises a pressure vessel and one or a plurality of spiral wound type membrane elements stored in the pressure vessel, the spiral wound type membrane element comprises a spiral membrane component including a perforated hollow pipe, a plurality of independent or continuous envelope-like membranes wound around the outer peripheral surface of the perforated hollow pipe and a raw liquid passage forming member interposed between the plurality of envelope-like membranes, a liquid-permeable material covering the outer peripheral portion of the spiral membrane component and an outer peripheral passage forming member entirely or partially covering the outer peripheral surface of the liquid-permeable material, the pressure vessel has a plurality of liquid ports, and the spiral wound type membrane module further comprises an introduction system introducing a washing liquid from at least one opening end of the perforated hollow pipe, a first takeout system discharging the washing liquid derived from the outer peripheral surface of the perforated hollow pipe through at least the outer peripheral portion of the spiral wound type membrane element and taking out the washing liquid from any one or a plurality of ones of the plurality of liquid ports of the pressure vessel, a supply system supplying a raw liquid into the pressure vessel through another one of the plurality of liquid ports, and a second takeout system taking out the raw liquid from the pressure vessel through the aforementioned any one liquid port or another liquid port.
In the spiral wound type membrane element of the aforementioned spiral wound type membrane module, at least the outer peripheral portion is not covered with a protective sheath but brought into an open state, whereby the raw liquid can be supplied from at least the outer peripheral side of the spiral wound type membrane element for performing filtration. In this case, contaminants are captured on at least the outer peripheral portion of the spiral wound type membrane element.
In the spiral wound type membrane module, the introduction system introduces the washing liquid from at least one opening end of the perforated hollow pipe in washing. The washing liquid derived from the outer peripheral surface of the perforated hollow pipe permeates through the envelope-like membranes and flows along the raw liquid passage forming member, to be discharged from at least the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element are separated from the spiral wound type membrane element and discharged from the one or a plurality of liquid ports through the first takeout system with the washing liquid. Thus, the contaminants captured on the membrane surface and at least the outer peripheral portion of the spiral wound type membrane element can be uniformly removed.
Further, the spiral wound type membrane module is provided with the supply system supplying the raw liquid and the second takeout system taking out the raw liquid, whereby a flow of the raw liquid can be formed axially along the outer peripheral portion of the spiral wound type membrane element. Thus, contaminants adhering to the membrane surface and at least the outer peripheral potion of the spiral wound type membrane element can be readily and reliably separated while the contaminants separated from the spiral wound type membrane element can be readily and reliably discharged, whereby the spiral wound type membrane module can be more stably run. The raw liquid may be axially fed along the outer peripheral portion of the spiral wound type membrane element before or after introducing the washing liquid from at least one opening end of the perforated hollow pipe for performing back wash reverse filtration. Alternatively, the raw liquid may be fed simultaneously with back wash reverse filtration.
In the spiral wound type membrane module, the washing liquid may be a permeated liquid, and the spiral wound type membrane module may further comprise a circulation system returning at least part of the permeated liquid taken out from the pressure vessel and at least part of the raw liquid taken out from the pressure vessel to the raw liquid supply side. In this case, the circulation system can circulate at least part of the permeated liquid and the raw liquid taken out from the pressure vessel, whereby the permeated liquid can be obtained with higher recovery.
These and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.